Solvent fractionation of fatty material



Sept 5, 1950 w. M. LEADERS Erm. 2,521,234

SOLVENT FRACTIONATION OF'FATTY MATERIAL IwwL FnAcUQNATorz T70 NEY Sept- 55 195.0 w. M. LEADERS ETAL 2,521,234

SOLVENT FRACTIONATION OF FATTY MATERIAL Patented Sept. 5, 1950 soLvEN'r raAc'rroNA'rroN or rA'r'rY MATERIAL William M. Leaders, Houston, Tex., and Frank A.

` Norris, Chicago, Ill., assiln ors, by menne assignments, to Swift & Company, a corporation of Illinois Application October 16, 1946, Serial No. 703,568

` This invention relates to thesolvent treatment of fatty materials. More particularly, the invention is concerned with a separation, or fractionation, ,process for the recovery `of vitamins, sterols and improved oil from fatty material.

Crude fatty material, such as vegetable and marine oils, contain tocopherols, or vitamin constituents, and sterols K in varying amounts. There are also present in crude fatty material such undesirable substances as color bodies, gums, resins and free fatty acids.` In treating crude fatty material, it is advantageous to recover therefrom the `tocopherols and sterols in concentrated form, while at the same time producing a neutral oil having improved qualities of color and flavor and `odor stability. Refined soybean oil particularly has the` tendency A,of acquiring undesirable flavor and odor characteristics, known as reversion," thus detracting from its value as a salad oil and as an ingredient in shortening and margarine products. Because of the `disadvantage of flavor reversion the use of soybean oil in edible products is limited and the,4 use thereof for edible purposes is less preferred to that of cottonseed oil, although the former is produced in greater quantities and hence is more available. Moreover, soybean oil is relatively rich in tocopherols and sterols. It is, therefore, advantageous to treat crude soybean oil to recover these materials therefrom in one fraction while simultaneously producing a stable and neutral oil in another fraction. In carrying out the process to produce a fraction rich in tocopherols and sterols and another fraction rich in improved oil, the steps in the process necessary to obtain one fraction often affect the nature of the other fraction. For example, decolorizing the oil before treating it to separate the tocopherols, tends to make the latter step more eilicient and results in a greater yield of these materials. On the other hand, the more complete the removal of the tocopherols, the greater the flavor stability of the oil appears to be.` Thus, in accomplishing the dual purposes of first obtaining vitamins, and second, an improved oil from 2 Claims. (Cl. E60-428.5)

i fatty oils with a liqueiled normally gaseous hydrocarbon under such conditions of temperature and pressure whereby the separation ofthe oils into a plurality of phases is effected. Further separation, or fractionation, of the phases to accomplish secondary separations may be carried out by altering the conditions of temperature., pressure and solvent ratio.

In -accordance with the invention, a liquefied normally gaseous hydrocarbon, such as propane, and crude fatty material are introduced into a decolorizing or fractionating tower. Temperature and pressure conditions, together with solvent to oil ratio, are so maintained in the tower that the propane shows selective solvent action for the oil while throwing out of solution the undesirable impurities, such as gums, resins, color bodies and phosphatides. The majority of the oil in the liquid propane is then charged to a second fractionating tower, wherein by altering the temperature and pressure and the amount of solvent, a secondary separation. of the oil into phases is accomplished. The phases are then separated and further fractionation thereof may 26 be carried out.

More specincallyit is contemplated to treaty crude glyceride oils with liquefied propane under crude fatty material, the steps in the process cooperate to produce the desired results.

`An object of the invention is to recover vitamins and sterols from glyceride oils while at the same time producing a more stable and neutral conditions of temperature and pressure and solvent to oil ratio such that decolorization of the oil iseected.` Along with the color bodies other impurities are removed from the oil in solution with the propane. The decolorized oil is subjected to fractionation under such conditions of solvent to oil ratio, temperature and pressure to selectively separate the vitamin material in one phase while leaving the bulk of the oil and sterols in the other phase. IGenerally the two phases thus produced are a lighter top phase, rich in vitamins, and a heavier bottom phase, containing a majority of the charged material including the sterols. The two phases are separated and the heavier fraction may be charged to a third operation wherein, under proper temperature and pressure conditions, a further fractionation of the oil may be effected to free the oil of free fatty acids and the remaining tocopherols and sterols. We have found that this separation makes possible the production of a highly neutral and stable oil.

- Alternatively, the invention may be carried out by a process whereby the oil is decolorized and the resulting decolorized oil subjected to a solvent separation or fractionation operation under conditions such that the vitamins, sterols and fatty acids may be separated as one phase from the bulk of improved oil contained in a second phase. The phase containing the vitamins, sterols and fatty acids is then subjected to a fractionating step, whereby the vitamins are separated from the fatty acids and sterols. According to one method of operation the crude oil in the presence of liquefied propane is subjected to conditions of temperature and pressure and solvent to oil ratio such that decolorization of the oil is effected. The color bodies together with other highly propane-'insoluble impurities are separated from the bulk of the oil. The decolorized oil and a major proportion of the solvent used in the decolorizer together with additional propane if necessary, is subjected to temperature and pressure conditions to decrease the solvent' action of the propane, thereby selectively dissolving the vitamins, sterols and free fatty acids, thus enecting two phases, one of which is relatively rich in vitamins, sterols and fatty acids,

i and the other rich in a decolorized, neutral oil.

apparatus for carrying out one embodiment of the invention wherein the tocopherols are sep-- arated prior to removal of free fatty acids and Figure 2 shows diagrammatlcally a modified type of apparatus for carrying out another embodiment of the invention wherein a fraction containing the tocopherols, sterols and free fatty acids is separated and is then treated for the separation of the vitamins from the sterols and free fatty acids.

Referring to Figure vl, crude oil, from a'source not shown, is pumped into decolorizer 18 by means of pump 2 through line 4 and preheater 5. Si-V multaneously with the introduction of oil into tower 8, about volumes of liquefied propane to 1 volume of oil from propane storage tank I5 is `pumped by means of pump I2 through preheater I4 and line I8 into tower 8. Temperature and pressure conditions in decolorizer 8 are such that two phases are formed, usu-ally a top lighter layerl consisting of a maior proportion of the oil in the bulk of the solvent, and a bottom heavier frac tion comprising the color bodies and other impurities. The bottom layer is withdrawn through line I9 to still 28, wherein the solvent is recovered and may be reused in the process. The top fraction is pumped from tower l by means 4 oil appearing in the bottom phase may be removed through line 3l controlled by valve 32. Alternatively, by suitable control of valves 32 and 34 on line 36 the bottom fraction, resulting from operations in fractionator 25, may be charged through line 35 and heat exchanger 21 to the top of tower 31. If desired, additional propane may be introduced into fractionator 31 through line 33 by appropriate manipulation of valve l1. In fractionator 31, operating temperatures are lowered to effect separation of a top layer relatively rich in free fatty acids and sterols and a bottom layer comprising a relatively stable, neutral oil. The top fraction is removed from fractionator 31 through line 4I provided with valve 42 and is introduced into still 43, wherein the solvent is removed from the fatty material for reuse in the of pump 23 through line 22 and preheater'24 into l tower 25. By suitable manipulation of valve I5 in line 28, additional solvent from tank I5 is .pumped into the -second tower 25 through line 28 and heat exchanger 2]. Conditions of tempera-l ture and pressure are so a usted in fractionator 25 that about 1 to 2 per cent of the charged ma' process. The bottom fraction is withdrawn through line 45, provided with valve 46, and is taken to still 48 for the separation of solvent from the oil. The towers may be provided with an electric or steam jacket or any other suitable means to aid in the control of temperatures lmaintained therein.

Referring to Figure 2, propane from tank 55 is pumped into fractionator 54 by means of pump 52 through preheater 53 and line 55 by suitable control of valve 51. Simultaneously with the introduction of propane into tower 54, crude oil from source not shown is introduced therein by means of pump 55 through line 55 and preheater 8I`. Operating conditions in tower 54 are such that two phases are formed. a small bottom phase containing the color bodies and other impurities. and a top phase containing the bulk of the oil in decolorized condition. The bottom phase is continuously withdrawn through line 83 and conducted to still 84, wherein the solvent may, be recovered and reused in the process. The decolorized oil is pumped by means of pump 85 through line 51 and preheater 58 into fractionator 15. Additional propane from tank 55 is introduced into tower 15 through line 12 by proper manipulation of valve 13. Operating conditions of temperature and pressure are increased in tower 15 in order to cause the formation of two phases, a top phase containing the vitamins,

through heat exchanger 83 by suitable control of valve 82. The temperature and pressure in tower 55 are increased so that a top fraction rich in Vvitamin materials and a bottom fraction rich in fatty acids and sterols are obtained. The vitamin fraction is withdrawn from fractionator 85 through line 55 and conducted to still 55, wherein the solvent is removed. 'I'he bottom fraction is withdrawn from fractionator 55 through line 58, conducted through heat exchanger 83 and introduced into still 55 wherein the solvent may be recovered and reused in the process.

We have found that decolorization of the crude oil may be effected by employing an amount of solvent in a ratio ranging from about l0 to 20 of solvent to l of oil by volume. Temperature conditions in the decolorizer may range from about F. to 170 F., with corresponding presauna sures of about 400 to 475 pounds per square inch absolute to keep the solvent in the liquid state. For most purposes, a temperature of about 160 l". and a'pressure of about 425 pounds per square inch absolute, with `a solvent to oil. ratio of about to l, have been found to be satisfactory. Under these conditions, about 2 vto 5 per cent of the charged oil is obtained as a bottom fraction.

In the second tower, or fractionator, temperatures of the solvent are so increased as to cause a majority of the vitamin material contained in the oil to be soluble in the propane while a majority of the oil is insoluble therein. We have found that about a 1 to 2 per cent cut obtained in the'top fraction is suitable forv most purposes, and may be effected by employing a temperature within the range of about 185 F. to 207 F., with corresponding pressures of about 540 to 630 pounds per square inch absolute.` The solvent to oil ratio may vary from about 25 to 1 to as high as 100 to 1. A temperature of about 200 F., with a pressure of about 600 pounds per square inch, and a solvent to oil ratio of about 50 to l, have been found satisfactory.

After leaving the second tower the oil, although decolorized, may still contain such impurities as free fatty acids which are less soluble in the propane than the vitamins under the operating conditions of the second tower. In order to produce a neutral oil these acids may be removed in the third fractionating step. Moreover, in

`neutral oil. Operating conditions in the third tower mayrange from about 180 F. to 195 F.

vwith a corresponding pressure range of about 510 to 590 pounds per square inch, and a solvent to oil ratio of 15 to 1` to 30 to l, depending on the may range from about 15 to 1 to 30 to 1, a ratio of about 25 to 1 being satisfactory; Under these conditions a top fraction containing from about 5 to" 15 per cent of the charged oil, includingthe vitamins, sterols and free fatty acids, and abottom fraction containing the improved oil, are obtained.

In order to separate the vitamin materials from the free fatty acids and sterols obtained in accordance with the last mentioned procedure, the fraction containing these substances is then subjected to a further fractionating treatment, involving an increase in temperature and pressure so as again to effect the formation of two phases, one of which is relatively rich in vitamins and the other in free fatty acids and sterols. In the third fractionating tower the solvent to oil ratio may range from about 25 to 1 to 100 to l. The temperature may range from about 185 F. to about 207 F. with a corresponding pressure range of about 540 to 630 pounds per square inch. A temperature of about 200 F. with a correspending` pressure of about 600 pounds per square inch and a solvent ratioof to 1 have been found satisfactory.

Although propane is the preferred solvent, we

, may employ other normally gaseous hydrocarbons or combinations thereof to good advantage,l

for example, ethane, propylene, isobutane, and butylene.

As examples of oils that may be used in accordance with the herein described process may be mentioned soybean, wheat germ, linseed, sunower, cottonseed, corn, rice bran, rapeseed, peanut and marine oils.

As an example of the invention, a crude peanut oil, having a tocopherol content of about 0.05 per cent, and being not darker than 19 F. A. C., was continuously charged to a fractlonating tower countercurrentto the simultaneous introduction therein of liquefied propane. The solvent was added in a ratio of 15 volumes of propane to 1 volume of crude oll.` An overhead take-olf temperature of 165 F. and a bottom temperature of 162 F. were maintained in the tower. Pressure about 4 per cent of the charged oil and containsize of the fractions desired. The size of the top fraction will be greater generally when it is deaired to.efl'ect a substantially complete removal of the unsaponiilable portion of the oil, and not' lso large when it is desired to remove merely other impurities, suchaas free fatty acids. Thus, for example, in the case of soybean oil the improved oil is obtained by removing substantially all oi the unsaponifiable portion therefrom, and in order to accomplish this result, operating condi- I tions are varied to achieve v,a large top cut `second tower (Fig- 2), and thus obtain the improved oil as a result of the second fractionating step, a bigger cut of the charged oil is made by maintaining the temperature between a range of about 180 F. to 195F. with a corresponding pressure range of about 510 to 590 pounds-per square inch. The preferred solvent to oil ratio ing color bodies, gums, phosphatides and other impurities insoluble in propane, was obtained.

. 'I'he overhead fraction, containing a majorityV of solvent and oil, was removed from the top of the tower and introduced directly into a second fractionatlng tower. The ratio of propane to oil was increased to 25 to 1 by the introduction into the tower of additional propane. The temperature was raised to 205 F. at the top of the tower and 201 F. at the bottom thereof. Apressure of 615 pounds per square inch was maintained on the solvent to keep it liquid. Under these conditions a top fraction was obtained containing about 0.5 per cent of the material charged to the tower. cent of the vitamins in the oil. The vitamin-free material had a `color of .35 Y and 3 Ron the Lovibond scale, and was suitable as an ingredient in shortening products.

As another example illustrative of the invention, crude lsoybean oil having a tocopherol con-v tent of about 0.11 per cent and a free fatty acid content of about 1 per cent, and being not darker than 25 F. A.C., was treated with 20 volumes of liquid propane in a countercurrent fractionating tower at an overhead take-off temperature `of F. and a bottom temperature of 157 F. and

This cut, on analysis, contained 96 per at a pressure of around 425 pounds per square inch. As a result oi' these operating conditions, a bottom fraction amounting to about 4 per cent of the charged oil and containing color bodies together with other propane-insoluble impurities, was obtained. The overhead fraction, comprising the remainder of the charged oil and the bulk of the solvent, was withdrawn from the top of the tower and introduced into a second fractionating tower near the top thereof. Additional propane was added to the second tower so that the overall solvent to oil ratio was 75 to 1. A. temperature in the tower of 200 F. at the top and 196 F. at the bottom, with a corresponding pressure of'600 pounds-per square inch. were maintained in the tower. Under these operating conditions a top fraction containing about 1.5 per cent of the charged oil was obtained. This fraction contained about 97 per cent of the tocopherols present in the original oil. The bottom fraction, containing the bulk of the oil, was introduced into a third fractionatipg tower and the solvent to oil ratio adjusted to about to 1. Temperatures in this fractionating step were lowered to about 190 F. and 185 F. at the top and bottom of the column, respectively, with a corresponding pressure of about 575 pounds per square inch. A top fraction containing 10 per cent of the oil charged to the tower was obtained. After removing the solvent, the i'ree fatty acid content of the cut was neutralized, and the resulting product used as an ingredient in paint. The bottom fraction contained about 85 per cent of the original charged soybean oil and had a color of 40 Y and 4 R on the Lovibond scale. This oil remained substantially odorless and tasteless after keeping at room temperatures for a period of 120 days. A refined control sample o1' the soybean oil reverted after l day at room temperatures.

As another example ofthe inventionnan amount oi.' linseed oil having a tocopherol content of about 0.07 per cent and a free fatty acid content of 8 per cent, and being not darker than 41 F. A. C.,

160 F. and the pressure at 425 pounds per square' inch. As a result of these operating conditions a. bottom fraction amounting to 3.5 per cent of the charged oil, containing the color bodies and other impurities, was obtained. The top fractioncoinprising the bulk o! decolorizedoil was continuously charged to a second fractionating tower togather with additional solvent, so that the solvent to oil ratio by volume was to l. The temperature in this tower was increased to 190 F., the pressure to 575 pounds per square inch to maintain the solvent in the liquid state. A top fraction amounting to 15 per cent of the charged material and vcomprising vitamins, sterols and free fatty acids was obtained. The bottom fraction, on the other hand, contained an improved neutral and relatively non-reverting oil. 'Ihe top fraction was then introduced into a third tower. Additional propane was added, so that the solvent to oil ratio was 50 to l. The temperature was raised to 195 F. with a corresponding pressure range of 590 pounds per square inch, under which conditions a top cut of about 1 per cent of the charged material was obtained. This top fraction was rich in vitamin materials, while the bottom fraction was relatively rich in fatty acids and sterols. The bottom fraction was subsequently subjected to molecular distillation to separate the was continuously charged to a fractionating tower countercurrent to the simultaneous introduction into the tower of propane in a ratio of 20 volumes of propane to 1 of oil. The tower was operated at a temperature of 155 F. under a pressure of 400 pounds per square inch. A 5 per cent bottom fraction containing the propane-insoluble impurities was obtained. A top fraction was charged to a second tower, togetherA with additional propane, in a ratio of to 1. In the second tower the temperature was raised to 195 l". and the pressure to 590 pounds per square inch, under which conditions a top fraction containing 1 per cent of the oil charged to the tower, having about 98 per cent of the tocopherols in the oil, was obtained. The bottom fraction was subjected to a third fractionating step, wherein the-solvent to oil ratio was '20 to l, and a temperature of 185 ll'., with a pressure oi' 540 pounds per square inch, was employed. Under these operating conditions,

a top fraction containing 14 per cent of. the oilv charged to the tower was obtained. The bottom fraction contained a substantially neutral oil, which was suitable for edible use. y

As a further example illustrating the operationV of the invention, a batch of soybean oil, being not darker than19 l". A. C. and having a free fatty acid content of 1.6 per cent and an unsaponiilable portion of 1.3 per cent, was continuously intro-v duced into a tower, into which there was also added liquid propane in aratio of 12 volumes to 1 of oil. The temperature was maintained at sterols from the fatty acids. A yield of 0.7 per cent of sterols based on the portion of unsaponiiiable material present in the original crude oil was obtained.

'Obviously, many modiilcations and variations of the invention, as hereinabove set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

a We claim:

"1. A method of producing a relatively nonreverting soybean oil havingsubstantially improved odor and flavor characteristics, which comprises: contacting in a fractionating zone a crude soybean oil having poor flavor and odor stability and containing color bodies and other nonsaponifiable impurities with from 10 to 20 times its volume of liqueed normally gaseous hydrocarbon at a temperature of between approximately and 170' F. and at a pressure of between approximately'400 and 475 pounds per square inch to form upper and lower phases, the lower of said phases containing between 2 and 5 per cent of the crude soybean oil having included therein substantially al1 the color body' impurities, and the upper of said phases comprising the remainder of the unimproved soy'- bean oil substantially free of color bodies; contacting the upper of said phases with additional liquefied normally gaseous hydrocarbon in a fractionating zone to increase the hydrocarbon-oil of the unsaponiable impurities; contacting the lower of said phases containing the major propor- -tion of the soybean oil with additional liquefied normally gaseous hydrocarbn sumcient to increase the hydrocarbon-oil ratio to between approxi-l mately 15:1 and 30:1 at a temperature of between approximately and 195 F. and a pressure of between approximately 510 and 590 pounds per square inch to form upperrand lower phases, the upper of said phases comprisingy a hydrocarbon solution of between 7 to 15 per cent of the soybean oil having included therein substantially all the nonsaponiable impurities remaining in the soybean oil, and the lower of said` fractions comprising a relatively nonreverting soybean oil substantially free of nonsaponable impurities; and recovering the lower of said phases substantially free of hydrocarbon and impurities, whereby a relatively nonreverting soybean oil having greatly improved flavor and odor characteristics isobtained.

2. A method of producing a relatively nonreverting soybean oil having substantially improved odor and flavor characteristics, which comprises: contacting in a fractionating zone crude soybean oil having poor ilavor and odor stability and containing color bodies and other nonsaponitlable impurities with between 10 and 20 times its volume of liquefied normally gaseous hydrocarbon at a hydrocarbon in a fractionating zone sulcient to increase the hydrocarbon oil ratio to between approximately 15:1 and 30:1 at a temperature of between approximately 180 and 195 F. and a pressure of between approximately 510 and 590 pounds per square inch to form upper and lower phases, the upper of said phases containing between approximately 5 and 15 per cent of the soybean oil having included therewith substantially all the remaining nonsaponiflable impurities in said vegetable oil, and the lower of said phases comprising the improved relatively nonreverting soybean oil substantially free of nonsaponiilable impurities; and recovering' the lower of said phases substantially free of hydrocarbon and ini-'- purities, whereby a relatively nonreverting soybean oil is obtained which has greatly improved ilavor and odor characteristics,

WILLIAM M. LEADERS. ,FRANK NORRIS.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 2,118,454 Schaafsma May 24, 1938 2,329,889 Ewing Sept. 21, 1943 2,394,968 Van Orden Feb. 12, 1946 2,432,021 Larner Dec. 2, 1947 

1. A METHOD OF PRODUCING A RELATIVELY NONREVERTING SOYBEAN OIL HAVING SUBSTANTIALLY IMPROVED ODOR AND FLAVOR CHARACTERISTICS, WHICH COMPRISES: CONTACTING IN A FRACTIONATING ZONE A CRUDE SOYBEAN OIL HAVING POOR FLAVOR AND ODOR STABILITY AND CONTAINING COLOR BODIES AND OTHER NONSAPONIFIABLE IMPURITIES WITH FROM 10 TO 20 TIMES ITS VOLUME OF LIQUEFIED NORMALLY GASEOUS HYDROCARBON AT A TEMPERATURE OF BETWEEN APPROXIMATELY 155* AND 170* F. AND AT A PRESSURE OF BETWEEN APPROXIMATELY 400 AND 475 POUNDS PER SQUARE INCH TO FORM UPPER AND LOWER PHASES, THE LOWER OF SAID PHASES CONTAINING BETWEEN 2 AND 5 PER CENT OF THE CRUDE SOYBEAN OIL HAVING INCLUDED THEREIN SUBSTANTIALLY ALL THE COLOR BODY IMPURITIES, AND THE UPPER OF SAID PHASES COMPRISING THE REMAINDER OF THE UNIMPROVED SOYBEAN OIL SUBSTANTIALLY FREE OF COLOR BODIES; CONTACTING THE UPPER OF SAID PHASES WITH ADDITIONAL LIQUEFIED NORMALLY GASEOUS HYDROCARBON IN A FRACTIONATING ZONE TO INCREASE THE HYDROCARBON-OIL RATIO OF BETWEEN 15:1 AND 100:1 AND AT A PRESSURE OF BETWEEN APPROXIMATELY 540 TO 630 POUNDS PER SQUARE INCH AT A TEMPERATURE BETWEEN ABOUT 185* AND 207*F. TO FORM UPPER AND LOWER PHASES, THE UPPER OF SAID PHASES COMPRISING APPROXIMATELY 1 TO 2 PER CENT OF THE SOYBEAN OIL, AND THE LOWER OF SAID PHASES CONTAINING THE REMAINDER OF THE SOYBEAN OIL INCLUDING THEREIN SUBSTANTIAL AMOUNTS OF THE UNSAPONIFIABLE IMPURITIES; CONTACTING THE LOWER OF SAID PHASES CONTAINING THE MAJOR PROPORTION OF THE SOYBEAN OIL WITH ADDITIONAL LIQUEFIED NORMALLY GASEOUS HYDROCARBON SUFFICIENT TO INCREASE THE HYDROCARBON-OIL RATIO TO BETWEEN APPROXIMATELY 15:1 AND 30:1 AT A TEMPERATURE OF BETWEEN APPROXIMATELY 180* AND 195*F. AND A PRESSURE OF BETWEEN APPROXIMATELY 510 AND 590 POUNDS PER SQUARE INCH TO FORM UPPER AND LOWER PHASES, THE UPPER OF SAID PHASES COMPRISING A HYDROCARBON SOLUTION OF BETWEEN 7 TO 15 PER CENT OF THE SOYBEAN OIL HAVING INCLUDED THEREIN SUBSTANTIALLY ALL THE NONSAPONIFIABLE IMPURITIES REMAINING IN THE SOYBEAN OIL, AND THE LOWER OF SAID FRACTIONS COMPRISING A RELATIVELY NONREVERTING SOYBEAN OIL SUBSTANTIALLY FREE OF NONSAPONIFIABLE IMPURITIES; AND RECOVERING THE LOWER OF SAID PHASES SUBSTANTIALLY FREE OF HYDROCARBON AND IMPURITIES, WHEREBY A RELATIVELY NONREVERTING SOYBEAN OIL HAVING GREATLY IMPROVED FLAVOR AND ODOR CHARACTERISTICS IS OBTAINED. 